448 THE JURASSIC DENUDATION 



During the Jurassic period the valleys in the folded 

 belt were greatly enlarged and deepened, so that the 

 Pre-Cape rocks became exposed in several areas south 

 of the Zwartebergen, where the chief rivers appear to 

 have had east and west courses. The rivers running 

 south from the main Colonial watershed have left no 

 trace of their passage through the mountain ranges in 

 Pre-Uitenhage times. The water flowing southwards 

 from the watershed probably drained away to the sea 

 in an easterly direction. This denudation received a 

 partial check in early Cretaceous times, so that the 

 longitudinal valleys in the folded belt became filled with 

 conglomerates, sandstones and shales, now represented 

 by the outliers of Uitenhage beds described in chapter 

 x. The cause of this may have been twofold, first, the 

 sinking of the land, and, secondly, the coming in of a 

 drier climate. That the former cause played an im- 

 portant part is evident from the fact that the marine 

 Sunday's River beds occupy an old valley between Port 

 Elizabeth and the Zuurbergen ; and the second of the 

 two causes is indicated by the nature of much of the 

 conglomerates and sands, the Enon type of the Uiten- 

 hage beds. It is not improbable that the Uitenhage 

 beds eventually covered the whole of the folded belt, 

 with the exception of the higher parts of the mountain 

 ranges ; there is reason to believe that in places the 

 lower passes in those ranges were buried under the 

 gravels and other rocks of the Uitenhage series. 1 As 

 we saw in chapter x., there is evidence to show that 

 marine beds were formed as far west as Knysna. 



1 Kogers, T. S. A. P. S., xiv., p. 375, 1903. 



